Cathode-ray device



Dec. 2,` 1958 E.' G. F. ARNoTT ET AL 2,863,084

cATHonE-,RAY DEVICE Filed Jui@ 27, 1955 CHfHaDE R4 Y.

Wam/0k INVENTUM 50h/HBD 6. F.' HBA/0mm! HEM/YY F'. IVE'Y BY UnitedStates Patent CATHODE-RAY DEVICE Edward G. F. Aruott, Upper Montclair,and Henry F.

Ivey, Bloomiield, N. J., assignors to Westinghouse Electric Corporation,East Pittsburgh, Pa., a corporation of Pennsylvania Application June 27,1955, Serial No. 518,321

Claims. (Cl. S15-1) This invention relates to cathode-ray devices and,more particularly, to a cathode-ray device which can operate withincreased brightness.

In many technical devices employing cathodoluminescence, an increase inthe attainable light output with out a corresponding increase for thepower required for the bombarding cathode-ray beam is advantageous. Ofcourse, the output of a cathode-ray excited phosphor can be increased byincreasing either the current in the electron beam or the acceleratingpotential for the electrons, but this cannot always be done withoutundesirable secondary effects. For example, if the beam current isincreased too much, the eifects of space charge become more pronouncedand the beam diameter will increase so as to impair the resolution. It,on the other hand, the beam potential is increased, it becomes morediilicult to deflect the beam and the power dissipated in the deliectingsystem increases. In addition, there is also the fact that the maximumpotential which may be used is limited by the secondary electronemitting property of the phosphor and many phosphors deteriorate undertoo intensive a bombardment.

It is the general object of the invention to avoid and overcome theforegoing and other diiculties of and objections to prior art practicesbythe provision of a cathoderay device which will have an increasedbrightness without an increase in either beam current or acceleratingpotential.

The aforesaid object of the invention, and other objects which willbecome apparent as the description proceeds, are achieved by providing acathode-ray device wherein a cathode-ray responsive phosphor is placedwithin the influence of an electric field while being simultaneouslyexcited to luminescence by cathode rays.

For a better understanding of the invention, reference should be had tothe accompanying drawing, wherein:

Fig. l is a plan view, partly in section, of a cathode-ray tubeincorporating a phosphor-influencing held-producing means in accordancewith this invention;

Fig. 2 is a sectional fragmentary enlargement of the phosphor andelectric held-producing window section of the tube as illustrated inFig. l;

Fig. 3 is an alternative embodiment, corresponding to Fig. 2, whereinthe phosphor material is imbedded throughout a dielectric material;

Fig. 4 is a further alternative embodiment, corresponding to Fig. 2,wherein the phosphor and dielectric material are included in separatelayers;

Fig. 5 is a sectional fragmentary enlargement, corresponding to Fig. 2,showing still another alternative embodiment wherein the phosphormaterial is deposited as a thin continuous lm and is separated from oneof the field-producing electrodes by means of the transparent windowportion of the tube.

Although the principles of the invention are broadly applicable to anycathodoluminescent type of device, the invention is usually employed inconjunction with a cath- CII ode-ray tube such as is commonly used intelevision receivers and hence it has been so illustrated and will be sodescribed.

With specific reference to the form of the invention illustrated in thedrawing, the numeral 10 indicates generally a cathode-ray tube having anenvelope which comprises an enlarged bulbous portion 12 and an elongatedneck portion 14. The neck portion contains an electron gun 16 forgenerating a stream of electrons adapted to be projected longitudinallywithin the envelope. A conductive coating 18 (e. g., an aqueoussuspension of graphite) is applied to the inner surface of the envelopeand extends to within a short distance of the electron gun 16 toconstitute an accelerating electrode by means of which an appropriateaxial field may be created within the envelope. The end of the envelopewhich is remote from the electron gun 16 is in the form of a flattenedtransparent window 20, which window has provided on its inner surface alayer 22 of phosphor material which is adapted to be excited to visibleluminescence by the impingement of electrons thereon and which ischaracterized by having an increased luminescent output whensimultaneously placed within the influence of an alternating eld, ashereinafter explained. Electron deflecting means, illustrateddiagrammatically as deflecting coils 24 and 26, may be provided adjacentan intermediate portion of the tube in order to cause the electron beamto scan sequentially the various elemental areas of the phosphormaterial carried by the window so as to develop a picture, such as atelevision picture, on the screen.

A thin transparent conductive layer 2.8, such as tin oxide, ispreferably carried on the interior surface of the envelope windowportion 20 and this thin conducting layer is adapted to be connected toa source of alternating current potential through electrical energyconnector 30 which is hermetically sealed through the envelope. Overthis thin conducting layer is placed the thin layer of phosphor'material22 and over the phosphor is placed an electr1cally conductive layer ofcathode-ray transparent material 34, such as a thin layer of aluminum,for example. This aluminum layer 34 constitutes `a second electrode andmay be connected to the envelope bulbous port1on conductive coating 18,as illustrated, or may be connected to a source of alternating currentpotential through a separate electrical connection adaptor. secondelectrode 34 may take the form 1f desired. Preferably the electrodes 28and 34 are substantially parallel to eliminate variations in fieldintensity.

As a specific example, the thin-transparent conductive layer 28 may beapplied as illustrated in Patent No. 2,522,531 to Mochel or Patent No.2,667,428 to Young. Other suitable thin-transparent coating layers mayalso be used. The phosphor material must be for the application and mustbe characterized by capabilof a wire mesh,

, ity of being energized to luminescence by cathode rays, can beenhanced by which cathode-ray luminescent output the simultaneousinuence of an alternating electric eld. In other words, when thephosphor alternating field and is simultaneously subjected to cathoderay bombardment, the output will be enhanced over that output which isrealized when the phosphor is subjected to the same cathode raybombardment alone, with the alternating eld removed. Suitable phosphorsfor this application are zinc sulfide-manganese activated,

zinc-'cadmium sulfide-manganese activated, zinc-cadmium sulfide-silverand manganese activated and zinc sulfidesilver and manganese activated.As illustrated in Figs. l through 4, these phosphors are in afinely-divided state, as is usual. 7 mole parts zinc sulfide, l molepart cadmium sulfide and activated by 4X 10H3 mole manganese. Such aphos-` phor may be prepared by ball-milling the aforementioned Theespecially selected is placed within an' As a specic example, thephosphor may be` 3 ingredients and firing in an oxygen-free atmospherefor aboutone hour at 11.00 C., for example. Following are furtherspecific examples:

Example I Example III ZnS: 4` l03 mole Mn and 0.5)(10'-2 mole Ag permole Mn Example IV per mole Mn The cathode ray transparent conductinglayer which constitutes the second electrode may be of aluminum, asheretofore noted, or other suitable material. Such materials arepresently utilized in the sohcalled aluminized television tubes.

The intensification of the cathode ray output appears to be essentiallyindependent of the frequency of the applied electric field and it ispreferable to use a frequency of 60 cycles per second as obtained fromthe A. C. mains, but this is by no means necessary and other frequenciesmay be used, if desired. The field strength required for the cathode rayintensification is not particularly critical and may be in the order of104 volts per centimeter, or less. For example, if, in the embodiment asillustrated in Fig. 2, the electrodes 28 and 3d are spaced apart 0.06mm., an applied voltage of 60 volts will produce a iield of 104 voltsper centimeter.

In order to prevent electric iield breakdown across the phosphormaterial, it may be desirable to imbed the phosphor material in anoneluminescent material having a relatively high dielectric strength,such as a polyamide [--COCH2CONH(CH2')6NH-l or methylmethacrylate. Suchan embodiment is illustrated in Fig. 3 wherein the phosphor material 22is imbedded throughout a separate dielectric material 36, whichphosphor-dielectric layer is placed between the electro-des 2S and 34 asin the embodiment of Fig. 2. The phosphor and dielectric may be mixed inthe ratio of 1 to 2, for example.

In Fig. 4 is illustrated a still further embodiment wherein the phosphorand dielectric material are incorporated as separate layers 22 and 5S.It 4is preferable that the phosphor material be positioned interiorlywith respect to the dielectric material in order that the cathode raysare not impeded, although if a cathode ray transparent dielectricmaterial is utilized, the arrangement of the separate layers does notmatter. The dielectric material ofthe embodiment as illustrated in Fig.4 may be a polyamide, as heretofore noted, or a transparent mica, forexample, to mention a few of the acceptable materials. The primaryrequirement of the dielectric material isthat it have a very low vaporpressure, preferably about 2x10*5 mm. mercury or less, for example, andrelatively high dielectric strength.

In Fig. 5 is illustrated a still further alternative embodiment whereinthe thin, transparent conductive layer of tin oxide 28a is placedexteriorly of the window portion of the envelope and the phosphormaterial is placed on the interior side of the envelope. The secondelectrode 34 is placed over the phosphor, as illustrated in theembodiment of Fig. 2. It is desirable that the electrode 28a beprotected by a plastic material, for example, although it may beunprotected and may be connected to the ground side of the A. C. supplyto eliminate shock hazard. In either of the embodiments of Fig. 2 orFig. 5, all that is required is that the layer of phosphor material becarried interiorly `with respect to the window 20, preferablycontinguous therewith and at most only separated therefrom by theelectrode 28, and be positioned between the electrodes in order to bewithin the iniiuence of the luminescent-enhancing alternating field. Thephosphor layer 22a, as illustrated in Fig. 5, may be deposited as a thincontinuous iilm, such as is illustrated in Patent No. 2,709,765 toKoller. Alternatively, the construction as illustrated in Fig. 5 mayincorporate a finely divided phosphor powder such as is illustrated inFigs. 2 through 4. Also, a thin continuous film of phosphor may be usedin place of the phosphor powder in the constructions illustrated inFigs. 2.and 4.

Utilizing constructional details as heretofore illustrated anddescribed, a phosphor screen brightness of arbitrary brightness unitshas been achieved under only cathode ray bombardment. Upon energizingthe electric (7Zn1Cd)S X104 mole Mn and 0.5X10 2 mole Ag 'zii field andcontinuing the cathode ray bombardment, a

light output of 126 arbitrary brightness units is achieved. Thus acathode ray enhancement of 26% has been achieved by the simultaneousinfluence of an alternating field.

It will be recognized that the objects of the invention have beenachieved by providing a cathode-ray device wherein the brightness isincreased.

While in accordance with the patent statutes, one embodiment of theinvention has been illustrated and described in detail, it is to beparticularly understood that the invention is not limited thereto orthereby.

We claim: v

l. A cathode-ray device comprising, a screen comprising iinely dividedphosphor material of one of the group consisting of zinc sulfide andzinc-cadmium suliide and activated by one of the group consisting ofmanganese and manganese-silver, means for applying an alternatingelectric field across said phosphor screen, and means `forsimultaneously bombarding said phosphor screen with cathode rays.

2. A cathode ray tube comprising an envelope having an enlarged bulbousportion terminating in a flattened transparent window and a neckportion, an electron gun mounted within said neck portion for generatinga stream of electrons adapted to be projected toward said window, aconductive coating applied to the inner surface of said bulbous portionand extending to within a short distance of said electron gun andadapted 'to act as an accelerating electrode for creating an axial fieldwithin said envelope, electron deflecting means positioned about saidneck portion and between said electron gun and said bulbous portion andadapted to have applied thereto a potential for causing said electronstream to scan sequentially elemental areas of said transparent window,said transparent window carrying a first transparent conducting layer, alayer comprising finely-divided phosphor` material carried interiorlyVof said window and in contiguous relationship therewith, a cathode rayVtransmissive second electrically conductive layer carried over saidphosphor layer, said phosphor exhibiting the property of sustainedluminescence under excitation by cathode rays and sustained enhancedluminescence under the simultaneous influence of an alternating electricfield, and said first and second electrically conductive layers beingadapted to have applied thereto an alternating potential.

3. A cathode-ray tube comprising an envelope having an enlarged bulbousportion terminating in a flattened transparent window and a neckportion, an electron gun mounted within said neck portion for generatinga stream of electrons adapted to be projected toward said window, aconductive coating applied to the inner surface .of said bulbous portionand extending to within a short distance of said electron gun andadapted to act as an accelerating electrode for creating an axial fieldwithin said envelope, electron defiecting means positioned about saidneck portion and between said electron gun and said bulbous por.- tionand adapted to have applied thereto a potential for causing saidelectron stream to scan sequentially elemental areas of said transparentwindow, said transpar-` ent window carrying a first transparentconducting layer, a layer comprising finely-divided phosphor materialcarried interiorly of said window and in contiguous relationshiptherewith, a cathode ray transmissive second electrically conductivelayer carried over said phosphor layer, said phosphor being one of thegroup consisting of Zinc sulfide and zinc-cadmium sulde and activated byone of the group consisting of manganese and manganese-silver, and saidrst and second electrically conductive layers being adapted to haveapplied thereto an alternating potential.

4. A cathode-ray device comprising, a screen including finely-dividedluminescent means which exhibits the property of sustained luminescenceunder excitation by cathode rays and sustained enhanced luminescenceunder 15 2,185,439

the simultaneous influence of an alternating electric field, means forapplying an alternating electric eld across said luminescent means, andmeans for simultaneously exciting said luminescent means with cathoderays.

5. A cathode-ray device comprising, a screen of dielectric andfinely-divided luminescent means, said luminescent means exhibiting theproperty of sustained luminescence under excitation by cathode rays andsustained enhanced luminescence under the simultaneous inuence of analternating electric field, means for applying an alternating electricfield across said luminescent means, and means for simultaneouslyexciting said luminescent means with cathode rays.

References Cited in the tile of this patent UNITED STATES PATENTS Re.22,734 Rosenthal Mar. 19, 1946 Hinderer Jan. 2, 1940 2,239,887 FerrantApr. 29, 1941 2,330,172 Rosenthal Sept. 21, 1943 2,650,310 White Aug.25, 1953 2,704,783 Sziklai Mar. 22, 1955

1. A CATHODE-RAY DEVICE COMPRISING, A SCREEN COMPRISING FINELY DIVIDEDPHOSPHOR MATERIAL OF ONE OF THE GROUP CONSISTING OF ZINC SULFIDE ANDZINC-CADMIUM SULFIDE AND ACTIVATED BY ONE OF THE GROUP CONSISTING OFMANGANESE AND MANGANESE-SILVER, MEANS FOR APPLYING AN ALTERNATINGELECTRIC FIELD ACROSS SAID PHOSPHOR SCREEN, AND MEANS FOR